Modern aircraft contain visual display systems that provide pilots with real-time terrain and weather information. In particular, visual display systems that provide dynamic, real-time terrain situational information including hazard awareness and avoidance information are well known. A typical aircraft cockpit display shows terrain data and potential hazards in a horizontal terrain elevation view or profile terrain elevation view relative to that aircraft's position, altitude and heading. For example, a terrain situation awareness display that illustrates a horizontal or plan terrain elevation view (i.e., “birds eye” or map view) and a profile terrain elevation view, is disclosed in U.S. Pat. No. 5,936,552 to Winchers, et al., which is incorporated herein by reference in its entirety.
However, a significant drawback of these earlier terrain situation awareness display systems is that they provide detailed terrain elevation information only for terrain elevations above a pre-selected “comfort zone”. Except for color coding large bodies of water and certain non-dynamic information (e.g., restricted air space, airport locations) on the display, these earlier systems eliminate terrain details below the elevation of the pre-selected “comfort zone”. Consequently, these earlier terrain situation awareness display systems are limited to the display of tactical information to which a pilot reacts in the short term.
Limitations of the earlier terrain situation awareness display systems have been overcome by a method for dynamically displaying terrain situation awareness information disclosed in commonly assigned U.S. Patent Application Publication No. U.S. 2004/0160341 A1 to Feyereisen et al. (“Feyereisen”), which is incorporated herein by reference in its entirety. In Feyereisen, an integrated display apparatus dynamically displays terrain situation awareness information over a selected distance relative to an aircraft's current position and altitude. The apparatus displays a color coded representation of a strategic portion of the terrain elevation data having an elevation less than a pre-selected strategic altitude threshold determined relative to and less than the current altitude data. The color coded representation of strategic terrain elevation data includes a monochromatic scale graduated as a function of terrain elevation relative to mean sea level. The apparatus also displays a color coded representation of a tactical portion of the terrain elevation data having an elevation greater than the pre-selected strategic altitude threshold. The color coded representation of a tactical portion of the terrain elevation data includes color coding as a function of terrain elevation relative to the altitude above ground data. As such, different colors are used to represent different tactical portions of the terrain elevation data. For example, one color (e.g., green) represents a safe portion of the tactical terrain elevation data having an elevation between the strategic altitude threshold and a pre-selected caution elevation below the altitude above ground data, a second color (e.g., yellow) represents a caution portion of the tactical terrain elevation data having an elevation between the caution elevation and the altitude above ground data, and a third color (e.g., red) represents a warning portion of the tactical terrain elevation data having an elevation greater than the altitude above ground data.
Existing aircraft display systems are capable of simultaneously displaying different color sets (e.g., safe/caution/warning) for absolute (relative to mean sea level) terrain elevation data and aircraft-relative (e.g., Enhanced Ground Proximity) terrain elevation data. For example, the color set displayed for absolute terrain elevation data is typically green/tan/brown, and the safe/caution/warning color set displayed for aircraft-relative terrain elevation data is typically green/yellow/red. However, a significant problem that arises with the simultaneous display of different color sets for absolute and aircraft-relative terrain elevation data is that pilots often become confused by the different color sets used, and in particular, by the similar colors used especially in the green and yellow/tan terrain elevation data color bands. Therefore, it would be advantageous to have a system and method that can eliminate color confusion between absolute terrain and relative terrain in aircraft displays. As described in detail below, the present invention provides such a system and method, which resolve the terrain color confusion problems encountered by pilots with existing aircraft displays and other prior art aircraft displays.